We have studied the control of DNA supercoiling in E. coli, and have found several regulatory interactions. Topoisomerase I stimulates the synthesis of both subunits of DNA gyrase, while the gyrase B protein represses the synthesis of gyrase A protein. The HimA protein, a known regulatory effector, stimulates gyrase A (but not B) protein synthesis. We have also sequenced the region around the start of the gyrB gene, and identified the beginning of the messenger RNA and of the protein chain.